In a stockpot heat olive oil over medium-high heat. Saute onions until soft, about 5 minutes.
Stir in black beans, pinto beans, kidney beans, tomatoes, vegetable broth, green bell pepper, chili powder, cumin and garlic powder; mix well and reduce heat.
Cover and simmer for 20 to 30 minutes stirring occasionally. Season to taste with salt and pepper. Serve hot.